In which of the following organisms does growth occur throughout their lifespan?

The growth involves

Define the following terms:
$(1)$ Growth
$(2)$ Growth rate

Efficiency index in the exponential phase of geometrical growth is the ability of plants to produce.

Assertion $(S)$: Growth occurs when anabolic processes exceed catabolic processes.
Reason $(R)$: Growth is the result of metabolism.
$(A)$ Both $S$ and $R$ are true,and $R$ is the correct explanation of $S$.
$(B)$ Both $S$ and $R$ are true,but $R$ is not the correct explanation of $S$.
$(C)$ $S$ is true and $R$ is false.
$(D)$ $S$ is false and $R$ is true.

In the sigmoid growth curve,the alphabets indicate the sequence of events. Choose the correct option where the alphabet specifies the event.